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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

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Question on rules for pressure vessel

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Question on rules for pressure vessel

Postby Ascension » Wed Feb 26, 2014 7:53 am

Hi

We are working on a water rocket that we would like to enter into the class A section. Our carbon fibre pressure vessel tube was made for us at a workshop. We then designed end caps ourselves and assembled the pressure vessel. Are we still within the regulation to compete?

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Re: Question on rules for pressure vessel

Postby bugwubber » Wed Feb 26, 2014 11:13 am

Ascension wrote:Hi

We are working on a water rocket that we would like to enter into the class A section. Our carbon fibre pressure vessel tube was made for us at a workshop. We then designed end caps ourselves and assembled the pressure vessel. Are we still within the regulation to compete?

Regards
Team Ascension


So here's the rule in question:

IV.   Pressure Vessel Rules
Pressure vessel is defined as the portion of the rocket containing the pressure (tank, end caps, and nozzle).
Pressure vessel must be fabricated by the rocket builder.
etc.

Don't think that leaves you much wiggle room but just my interpretation.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Wed Feb 26, 2014 3:40 pm

So that means that you can't by ftc tubing and use it because it was not fabricated by the rocket builder. Think about that. I think it is fine.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Wed Feb 26, 2014 3:42 pm

You can't use FTC tubing for a submission it would mean. Neither pop bottles. They go against the rules too. I see no difference between Coca Cola giving this guy bottles and a man at a workshop giving him a tube.
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Re: Question on rules for pressure vessel

Postby bugwubber » Wed Feb 26, 2014 4:31 pm

Water Rocket Expert wrote:You can't use FTC tubing for a submission it would mean. Neither pop bottles. They go against the rules too. I see no difference between Coca Cola giving this guy bottles and a man at a workshop giving him a tube.



The other rules make it clear you can use those components but since in this case, they are technically utilizing a "portion of an existing high pressure enclosure"..no.

But your and my opinion are not what matters here. This is really for WRA to answer.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Wed Feb 26, 2014 4:43 pm

Well yeah they do need to but maybe the workshop makes them for other things besides this. Maybe it was not designed for high pressure even though it can withstand. I could be wrong, but as far a I am concerned, it sounds legit to me.
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Re: Question on rules for pressure vessel

Postby WRA2 » Wed Feb 26, 2014 5:49 pm

Ascension wrote:Hi

We are working on a water rocket that we would like to enter into the class A section. Our carbon fibre pressure vessel tube was made for us at a workshop. We then designed end caps ourselves and assembled the pressure vessel. Are we still within the regulation to compete?

Regards
Team Ascension


I appreciate your honesty but a "manufactured carbon fiber tube" that was manufactured purposely to be your rocket would not qualify under the rules. Can you provide more details about the "workshop" Did you build the tube yourself (or the team members) using a workshop or did you order it from a company that specializes in making carbon fiber tubes that are used as a pressure vessels? That makes a difference. Re-purposing a CF tube that was used for something else say a bicycle frame would be allowed too. If we did not have this rule, the competition would turn into who has the most cash and can order the biggest, strongest tube from a professional manufacturer. The purpose of this competition is to design and build the best rocket.
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Re: Question on rules for pressure vessel

Postby WRA2 » Wed Feb 26, 2014 6:06 pm

Water Rocket Expert wrote:You can't use FTC tubing for a submission it would mean. Neither pop bottles. They go against the rules too. I see no difference between Coca Cola giving this guy bottles and a man at a workshop giving him a tube.


Sounds like "The Expert" has some more sour grapes. We heard these same arguments years ago (usually from people that were looking to gain some kind of advantage). Those people were suggesting that the rule meant that teams would have to make their own rocket from individual elements and chemicals. The idea of the rule is to prevent a team from ordering a rocket from "pressure vessels r us" and competing in the competitions. Re-purposing a lamp protector is fine so is purchasing carbon fiber, fiberglass, or Kevlar cloth and epoxy and "rolling your own" tube.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Wed Feb 26, 2014 6:53 pm

Okay that clears it up for me. What the WRA2 says goes and that's fine. To bad though for Ascension.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Wed Feb 26, 2014 6:58 pm

I guess the WRA2 is kinda right because their has to be a limit somewhere. We obviously can't make pop bottles but when you think about the competition for the most cash, the idea sounds more real.
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Re: Question on rules for pressure vessel

Postby Spaceman Spiff » Thu Feb 27, 2014 1:57 pm

Water Rocket Expert wrote:I guess the WRA2 is kinda right because their has to be a limit somewhere. We obviously can't make pop bottles but when you think about the competition for the most cash, the idea sounds more real.


The way I read it, you can use an off-the shelf non metal tube for a legal rocket, but an off-the-shelf pressure tank would be forbidden. There are plenty of places on the internet you can buy cylinders and tube shapes made from fiberglass and carbon that could be turned into a rocket.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Thu Feb 27, 2014 3:13 pm

Would they be legal to use. If so what is the difference between that and one bought at a shop. If the shop was commercial and designed it for high pressure for that purpose, well then it is illegal for the rules.
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Re: Question on rules for pressure vessel

Postby bugwubber » Thu Feb 27, 2014 4:14 pm

Water Rocket Expert wrote:Would they be legal to use. If so what is the difference between that and one bought at a shop. If the shop was commercial and designed it for high pressure for that purpose, well then it is illegal for the rules.


So lets say I went to Stuffmart and they had for sale Carbon Fiber High Strength Pipes. And fittings too. And all I had to do was plunk down $1000 for a 10ft pipe and its fittings and some glue. Boom, I'm a shoe in for the high altitude competition.

And here you are with a teenager's budget working on your fishing line reinforced bottles. You're gonna put a year of work into getting your bottles to hold enough pressure and I'm going to spend one evening gluing premade parts together. At the end of the year, you will have much more knowledge about making HP rockets than I, but I'll hold the title because I had the money to hit the Easy button.

Is that a fair competition?

It doesn't mean that we can't both still have fun, but perhaps we shouldn't be in the same category when it comes to competitions.

Now, SHOULD there be a highest alt no matter how you got it category? Well in a way it already exists- the Personal/Team Best.
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Re: Question on rules for pressure vessel

Postby Water Rocket Expert » Thu Feb 27, 2014 4:35 pm

Well said and I understand but did USWR wrap their tube from carbon fiber, or was it a carbon pipe to begin with. Someone needs to create a poll for this topic.
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Re: Question on rules for pressure vessel

Postby bugwubber » Thu Feb 27, 2014 9:11 pm

Water Rocket Expert wrote:Well said and I understand but did USWR wrap their tube from carbon fiber, or was it a carbon pipe to begin with. Someone needs to create a poll for this topic.


They had to submit their info to WRA and WRA has given it their stamp of approval so this is a dead question. If you look around on the web, youll find filament wound carbon pipe in the strength and dimensions needed is almost at unicorn status.
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